The invention relates to a procedure for detecting and classifying impurities in longitudinally moving inspection material of textile fibres.
Such impurities are to be understood to be, in particular, fibres having other properties, for example, having a colour other than that to be attributed to the basic material. They are also to be understood to include, however, impurities which generally interfere with the normal arrangement of the fibres of the basic material, are not of fibrous constitution, or even constitute actual foreign bodies.
Such a procedure is known from WO 01/92875. In that case, two different properties of the inspection material, such as the capacitance variation in an electric field and the reflection of light by the inspection material, are to be continuously measured. Deviations of measurement values of these properties from a standard value are measured and stored in memory, and can be recorded in a coordinate system in which values for coordinates, which represent both properties, are entered. Through the predefinition of appropriate threshold values or limits for both properties, impurities of a first type can be distinguished from impurities of a second type, and also be selectively subjected to different subsequent processing. In this case, the signals for both properties are each separately compared with their own assessment specifications. The continuous evaluation enables, for example, impurities of a vegetable nature to be distinguished from impurities of a non-vegetable nature, and to be eliminated from the inspection material in a selective and differentiated manner.
A disadvantage of this known procedure is that, in particular, although it is very suitable for distinguishing certain impurities from one another, out of a greater selection of possible impurities it can at best be used for identifying one impurity or an entire group of impurities, without distinguishing between them.